A man is an adult male human. Prior to adulthood, a male human is referred to as a boy.
A man with medium skin tone, of medium build, and with facial hair
Most men are heterosexual (sexually attracted to women) and cisgender (were assigned male at birth and have a male gender identity).
Michelangelo's David is the classical image of youthful male beauty in Western art.
Two men playing a board game
An adult is a human or other animal that has reached full growth. The biological definition of the word means an animal reaching sexual maturity and thus capable of reproduction. In the human context, the term adult has meanings associated with social and legal concepts. In contrast to a non-adult or "minor", a legal adult is a person who has attained the age of majority and is therefore regarded as independent, self-sufficient, and responsible. They may also be regarded as a "major". The typical age of attaining legal adulthood is 18, although definition may vary by legal rights, country, and psychological development.
An adult human male (left) and female (right)